Diamond and cubic boron nitride (cBN), as materials with very similar structure, exhibit, remarkable structural and electronic properties. Due to their extreme hardness both materials are the choice superabrasives in machine tooling operations. As wide gap semiconductors, diamond and especially cBN are very promising materials, in the form of thin films, for a future generation of high- temperature, high-pressure and radiation-resistant fast microelectronic devices, optoelectronic applications and field effect devices. Despite the crucial influence of the lattice defects (intrinsic or impurity type) on the physical and materials related properties, the defect characterization of these
materials, especially as crystalline films, has begun only recently to receive a more systematic attention. In addition, nowadays diamond and cBN can be both p- and n-type doped, but the current results are still very far from the expectation as concerns the carrier mobility, doping reproducibility and understanding how dopants are incorporated. This concerns specially the n-type diamond and p- type cBN. In addition the preparation of cBN in the form of thin films is still a technological endeavor. For electronic applications, even the hexagonal BN is a very wide gap interesting material of which the main properties are unknown.